1. Research Team for Promoting Independence and Mental Health, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo 173-0015, Japan
2. School of Health Sciences, Meikai University, Chiba 279-8550, Japan
3. Department of Dental Hygiene, University of Shizuoka, Shizuoka Junior College, Shizuoka 422-8021, Japan
4. Department of Preventive Dentistry, Faculty of Dental Medicine, Graduate School of Dental Medicine, Hokkaido University, Hokkaido 060-8586, Japan
5. Gerodontology, Department of Oral Health Science, Hokkaido University, Hokkaido 060-8586, Japan
6. Dentistry and Oral Surgery, Tokyo Metropolitan Geriatric Hospital, Tokyo 173-0015, Japan